Oxo-titanylphthalocyanine crystal, method for producing the same, and electrophotographic photoreceptor

Abstract

The invention provides an oxo-titanylphthalocyanine crystal which is stable, is superior in dispersibility in a photoreceptive layer and efficiently contributes to improvements in sensitivity and charge retention rate of an electrophotographic photoreceptor when it is used as a charge generating agent, a method for producing the oxo-titanylphthalocyanine crystal, and an electrophotographic photoreceptor. The oxo-titanylphthalocyanine crystal has predetermined optical characteristics and thermal properties and is produced by a production method including the following steps (a) to (d): (a) a step of dissolving a crude oxo-titanylphthalocyanine crystal in an acid to obtain an oxo-titanylphthalocyanine solution; (b) a step of adding the oxo-titanylphthalocyanine solution dropwise in a poor solvent to obtain a wet cake; (c) a step of washing the wet cake with an alcohol having 1 to 4 carbon atoms; and (d) a step of stirring the washed wet cake under heating in a nonaqueous solvent to obtain an oxo-titanylphthalocyanine crystal.

1. A method for producing an oxo-titanylphthalocyanine crystal having a main diffraction peak at a Bragg angle (2θ±0.2°)=27.2° in a CuKα characteristic X-ray diffraction spectrum and one peak in a temperature range from 270 to 400° C. other than the peak derived from vaporization of adsorbed water in differential scanning calorimetric analysis,
 the oxo-titanylphthalocyanine crystal having the absorbance for light which is within a range from 0.01 to 0.08 in a wavelength of 400 nm and which is measured for a filtrate obtained by filtering of a suspension including the oxo-titanylphthalocyanine crystal, when adding the oxo-titanylphthalocyanine crystal in an amount by weight of 1.25 parts based on 100 parts by weight of a mixed solvent of methanol and N,N-dimethylformamide (methanol:N,N-dimethylformamide=1:1 (by weight ratio)) to prepare the suspension, and the oxo-titanylphthalocyanine crystal being produced by a production method comprising the following steps (a) to (e): 
 (a) a step of performing a pre-acid treatment in which a produced oxo-titanylphthalocyanine compound is added in an aqueous organic solvent which is at least one type selected from the group consisting of alcohols, N,N-dimethylformamides, propionic acid, acetic acid, N-methylpyrrolidone and ethylene glycol, the mixture is stirring in the condition of a fixed temperature of about 70 to 200° C. for about 1 to 3 hours and stabilizing in an aqueous organic solvent in the condition of a fixed temperature range of about 10 to 50° C. for 5 to 15 hours; 
 (b) a step of dissolving a crude oxo-titanylphthalocyanine crystal in an acid to obtain an oxo-titanylphthalocyanine solution; 
 (c) a step of adding the oxo-titanylphthalocyanine solution dropwise in a poor solvent to obtain a wet cake; 
 (d) a step of washing the wet cake with an alcohol having 1 to 4 carbon atoms; and 
 (e) a step of stirring the washed wet cake under heating in a nonaqueous solvent to obtain an oxo-titanylphthalocyanine crystal. 
 
     
     
       2. The method for producing the oxo-titanylphthalocyanine crystal according to  claim 1 , wherein the acid used in the step (a) is at least one type selected from the group consisting of concentrated sulfuric acid, trifluoroacetic acid and sulfonic acid. 
     
     
       3. The method for producing the oxo-titanylphthalocyanine crystal according to  claim 1 , where the poor solvent used in the step (b) is water. 
     
     
       4. The method for producing the oxo-titanylphthalocyanine crystal according to  claim 1 , wherein the alcohol having 1 to 4 carbon atoms which is used in the step (c) is at least one type selected from the group consisting of methanol, ethanol and 1-propanol. 
     
     
       5. The method for producing the oxo-titanylphthalocyanine crystal according to  claim 1 , wherein the wet cake was washed with the alcohol having 1 to 4 carbon atoms, and further washed with water in the step (c). 
     
     
       6. The method for producing the oxo-titanylphthalocyanine crystal according to  claim 1 , wherein the oxo-titanylphthalocyanine crystal has a main diffraction peak at a Bragg angle (2θ±0.2°)=27.2° in the CuKα characteristic X-ray diffraction spectrum measured after it is dipped in an organic solvent for 24 hours and no peak at 26.2°.